Genetics Study

Finds Genes That Cause Trigeminal Neuralgia

Introduction by Michael Pasternak

In 2012 The Facial Pain Research Foundation approved a research study to find the genes responsible for trigeminal neuralgia.

While each of our Foundation’s scientific projects are valuable, the one that has been the most awesome and challenging for me has been the Genetics/DNA project. Dr. Doug Anderson (FPRF Director of Research) and I have had to communicate with scientists from four different countries (including Joanna Zakrzewska in London) and Collection Centers in 9 different cities in three countries! Doug has spent months on this project “everyday”! He has also had to communicate with additional scientists interested in our efforts and has done this while still overseeing the creation and development and evaluation of all of our Foundation’s other projects! How did we and he get so lucky?

While Doug has overseen and worked through the science some of our other Volunteers have been involved in working with the DNA Collection Centers, working through intellectual property problems, legal questions, raising the funds to pay for all of this, communicating to patients to give their DNA, creating PR pieces for the public to participate, keeping track of collection numbers, certifying completion of collections and data sent to OHSU and Rutgers, and making payments to the Collection Centers for their efforts. This project has been an enormous accomplishment. No Volunteer Foundation or organization has ever done this before! All completed while we grew our outstanding scientific project numbers to six and linked with two venture capital funded research projects.

The FPRF has spent over $650,000 of funds raised by our Volunteers and donors on this project. The FPRF Trustees have committed another $325,000 to complete the project in the next year.

So, now we have a team of scientists who have worked hard using their unique skills and understandings and have presented a report to our Trustees and asked to go forward to replicate the study during the next year to prove that what they have found are really the genes that will lead us to finding the cures. The Cilker Genetics/DNA Research Report has arrived. It is remarkable. We are extremely thankful to Drs. Devor, Burchiel, Seltzer, Diehl and Anderson for all of their voluntary efforts to create these findings. We are also truly thankful for Our Trustees and all of our Volunteers who helped raise the necessary funds to complete the tasks. This is an exciting time for all of us committed to ending the pain for all TN and related neuropathic sufferers.

The Following is a Non-Technical Summary Report…The detailed full Scientific Report has been presented to the Foundation Trustees and contains confidential information. It will be confidential until the replication of findings has been completed. Following the report is an article by Dr. Scott Diehl for general distribution.

The main goal of our study is to find genes that cause “Classical” Trigeminal Neuralgia Type 1 (TN1). This information will help clinician-scientists find cures that relieve patients’ severe chronic pain or prevent it from developing. Thus far, we’ve searched the genetic material (DNA) of TN1 patients at over a million places where people are known to differ from one another in their DNA letters (A, T, G or C). On average, any two people have about five million DNA differences between them. Most differences have no effect on health, but some cause or predispose to disease. Our challenge is to find the “needles in a haystack” that cause TN1, hidden among the millions of differences with no relation to TN1. We do this by comparing DNA of TN1 patients (cases) with that of people who do not have TN1 (controls).

Our initial search focused on 348 Caucasian TN1 patients, a modest sample size for human genetic studies today. Nevertheless, we are delighted to report discovery of several regions in the human genome with promising evidence they may harbor genes causing TN1. Some regions include only one gene, but there are 17 genes in the genome location with the strongest statistical support, including 3 with biological functions involving nerve degeneration, excitability of neurons or responses to nerve injury. These genes are strong suspects, but to determine which genes actually cause TN1we need a combination of: a) more genetic data of the kind we have already been gathering, and b) information from a complementary approach that uses high speed DNA sequencing. This further research is absolutely necessary before our initial discoveries are ready for testing in animals or translation to the clinic.

First, we must be absolutely certain our TN1 patients and controls do not happen to be very different by chance alone, but that the DNA differences occur because mutations hidden in the regions actually cause TN1. To do this, we will repeat our experiment a second time and see if we get the same results. We will analyze variation across the human genome for a new set of TN1 patients and controls using the most advanced genomic assays now available, more than doubling our sample size. If the same genome regions are again different in TN1 patients compared to controls (like lightning striking in the same place twice), this replication will confirm that TN1 disease-causing genes are indeed located there. Some regions have initial statistical support stronger than others, so these are more likely to be confirmed, but only by doing the assays and carefully evaluating what the data tell us will we know for sure which regions are confirmed. We do not expect all of our initially positive regions to be confirmed, but even if only one region is strongly confirmed this will be an extremely important advance, not only for TN1 but for the entire biomedical field of neuropathic pain in general. 2 Submitted January 3, 2018

Moreover, it is not enough to just find regions of the genome that harbor genes that cause TN1 – we also have to identify the specific genes and mutations in these genes that cause them to biologically malfunction, as this information is essential for translation to new therapies. It is possible that some of the mutations that cause TN1 are extremely rare, found only in TN1 patients and their close relatives. To discover additional TN1 genes and TN1-causing mutations, including those that are very rare, we will use the latest technologies for “reading” the DNA sequence of the entire human genome in a select subset of our TN1 patients. This method is called Next Generation Sequencing (NGS), and we propose to perform this assay for 100 TN1 patients.

Combining our previously-studied as well as our new TN1 cases gives us a sample of approximately 900 TN1 cases, of mostly Caucasian racial origin but with some non-Caucasians included too. Combining these with a similar number of controls will provide us with substantially increased statistical power to ask several very important questions such as the following: Do different genes cause TN1in young patients versus those who experience their first symptoms when older? (We already started to ask this first question in a limited way in the first phase of our research and with a larger sample can address this more rigorously.) Are there different genetic effects in males versus females, as found in many other genetic diseases? Are there different genes causing TN1 in the (typically younger) patients without vascular compression of their trigeminal nerve compared to patients whose trigeminal nerve has been damaged by years of vascular compression?

Our research may lead to a more complex picture of TN1 as being caused by not just mutations of just one gene, but in fact mutations found in several different genes may be associated with various subtypes of TN1. Genetics may reveal TN1 clinical subtypes that we currently do not even recognize exist, as has been found in numerous other neurological conditions including the epilepsies and the many forms of ataxia caused by different genes. While our primary goal remains identifying gene mutations that cause TN1, the research described here for the next phase of our study may also identify genetically distinct subgroups of TN1 patients as a very important secondary benefit of our genetic approach. Progress towards a cure (or, more likely, “cures”) will be more rapid and have greater chance of success if it is built on a foundation of knowledge about what is really going on biologically in different TN1 patients rather than if forced into a “one size fits all” therapeutic approach.

Project Timeframe: With adequate funding all research can be completed within one year. 3 Submitted January 3, 2018

Genetics Study

Brings Precision Medicine

To Trigeminal Neuralgia

By Scott Diehl

The Genetics Study team supported by the Foundation has completed a search of over one million locations in the DNA of 348 Trigeminal Neuralgia (TN) patients. This “Big Data” effort has pointed to genes affecting excitability of neurons, nerve degeneration and responses to nerve injury. These genes are very strong suspects, and the team will now gather additional information from more patients and from a complementary approach that uses high speed DNA sequencing.

In the team's next effort, these genes will be tested in a new set of TN patients.

If the same results are found again, this replication will be like lightning striking in the same place twice and confirm that mutations in these genes cause TN in some patients. These next steps are essential to confirm the initial findings and they may also reveal additional genes not detected with a strong enough signal in the initial search. Once confirmed, these discoveries will then be ready for testing in animals and translation to patients in the clinic.

The genetics data gathered thus far are painting a complex picture of TN as being caused by not just mutations in any one gene. It appears more likely that several different genes are involved in different patients, a phenomenon known as “genetic heterogeneity.” For example, one of the most strongly supported genes is important only for TN patients whose symptoms first appeared after age 55. A different gene with different biological functions is implicated in patients who developed TN at a younger age. Genetic heterogeneity has been found in other neurological conditions including the epilepsies and the many forms of ataxia caused by different genes. This strategy, known as Precision Medicine, is a major US and International effort getting underway focusing on nearly all human health problems today (https://allofus.nih.gov/).

While the primary goal of the genetics study is to identify gene mutations that cause TN, this research may also identify genetically distinct subgroups of TN patients as a very important secondary benefit. Progress towards a cure (or, more likely, “cures”) will be more rapid and have greater chance of success if built on a foundation of knowledge about what is really going on biologically in different TN patients rather than if forced into a “one size fits all” therapeutic approach.

The Genetics Study Team supported by the Foundation is an international collaboration of leaders in the fields of neurosurgery, pain biology and human genetics at Oregon Health and Science University (Dr Kim Burchiel), The Hebrew University of Jerusalem (Dr Marshall Devor), the University of Toronto (Dr Ze’ev Seltzer) and Rutgers School of Dental Medicine (Dr Scott Diehl). Numerous additional locations have provided valuable assistance with recruiting patients.